Priming is an important part of home brewing. Without it you won’t have much foam or aroma and your brew won’t look at lot like beer.
So here’s a guide to priming sugar including how to use just the right amount.
The importance of carbonation is sometimes overlooked, but it’s one of the most noticeable sensory aspects of beer.
It affects appearance, smell and mouthfeel and, I suspect, flavour. So it’s important to get it right.
The usual way to carbonate bottled beer is by adding priming sugar.
On the face of it the principles are simple: treat the yeast to a little more sugar while they’re in the bottle and they’ll reward you with gas.
But while there are rules of thumb about how much priming sugar to add – 4 oz (113 g) per 5 gallons (19 litres) or, the old school version, a teaspoon per bottle – I find that the results often vary.
Fed up with the situation I decided to find out more about it, and have prepared this guide explaining what it’s all about.
It may not sound like the most riveting subject for a blog post but there’s no doubt it’s useful stuff when brewing.
(I’m talking about carbonation in bottles with priming sugar. This Brew Strong show contains information on force carbonation in kegs, if you’re interested in that.)
What is Priming Sugar?
As I’ve already mentioned, priming sugar is sugar added to home brew before packaging to give it gas and head.
Although carbon dioxide is produced throughout the main fermentation most of it escapes through the airlock, carrying away unwanted elements as it goes.
So when you bottle the beer, to all intents and purposes it’s flat.
By adding priming sugar as the beer goes into the bottles, you encourage the yeast to generate more carbon dioxide. This time, because the bottles are sealed, it becomes part of the beer.
Most sugars work for priming although some are better than others.
Types of Sugar To Use For Priming Beer
More often than not brewers want to add priming sugar without changing the beer flavours.
Table and corn sugar are popular, flavourless options. But you can use more or less anything.
Sometimes you may want the priming sugar to add extra layers of flavour. I’ve primed with honey, for example, attempting to maximise those flavours in (unsurprisingly) a honey beer.
Similarly, I often use brown sugar in dark ales and bitters because I think those flavours marry well.
Perhaps the impact is negligible, but it feels right when the ingredients are consistent throughout the brew process.
When choosing priming sugar, think of the flavours you want to add. If it’s not important, use white sugar.
Priming Sugar and Amount of Gas
You can describe the amount of gas in a beer with the term “volume”. The unit is the same as the one you use to measure your beer, usually gallons or litres.
1 volume = 1 litre/1 gallon of CO2 in 1 litre/1 gallon of beer
The more priming sugar you add the more gas you get. But how much do you want?
While to some extent it’s a matter of taste, different types of beer traditionally have different amounts of carbonation.
This table is adapted from guidelines in How To Brew, and shows typical volumes of CO2 in different types of beer:
Knowing how much gas is needed, you can work out how much priming sugar to use to get it.
Unfortunately, and as ever, it’s not entirely straightforward because when the beer comes out of the fermenter it actually contains some residual CO2.
CO2 After Fermentation and the Effect of Temperature
Carbonation of liquids is governed by Henry’s Law.
It gets complicated quickly (and is beyond my ability or desire to go into it in much detail!), but the key thing is that the amount of gas in the beer depends on the temperature and pressure.
As I understand it, over time the gas dissolved in the liquid will reach equilibrium with it’s surroundings. Inside the fermenter the head space is almost entirely CO2 so in the liquid there’s a good amount of gas.
Liquid is able to take in more gas at lower temperatures, so the warmer the beer the less gas. I wonder if this explains why it’s traditional for lagers to be carbonated higher than ales.
In any case, it’s why most priming sugar calculators ask for bottling temperature.
Priming Sugar Calculations
This Home Brew Digest article is a good primer on carbonation in general, and explains how to calculate the amount of priming sugar needed to achieve a certain amount of gas.
It includes a table of the CO2 already in the beer, according to temperature, which I’ve interpreted here:
You can use that information to work out how much gas to add:
According to the article, it takes 4 grams of table sugar (sucrose) per litre to produce 1 volume of CO2, so:
To get 2.5 volumes of gas into 20 litres of beer at 14°C, for example:
(These conversion tables go between grams and ounces, gallons and litres).
Although you can calculate manually, it’s most common to use brewing software to work out priming sugar amounts.
I find the Northern Brewer one useful because it includes a wide variety of fermentables.
I cross checked a few sample calculations with the above formulae and they more or less coincide.
As I researched this post I came across this article which elaborates on the idea, making it clearer.
However, in the second article the alleged contribution of sucrose to carbonation is different, 3.5 g per litre instead of 4 g.
As usual the various disagreeing sources mean that to get to the bottom of it it’s best to test on your own set up and adjust according to experience.
I feel a side by side experiment coming on.
Having said that, I’m not especially bothered by approximations as everything in my process is rough and imprecise. If it’s different on your system I don’t believe you!
More than anything, looking at sample calculations can help you understand the principles:
- More sugar makes more gas
- Priming at warmer temperatures requires more sugar
Priming Sugar Quick Reference Guide
Using the Northern Brewer calculator I’ve extracted some commonly used priming sugar amounts to save time on brew day.
I’ve calculated for low, medium and high carbonation. I don’t believe I measure temperature accurately enough, or therefore know how much carbonation’s already in the beer, to bother being more precise than that.
Bear in mind that I’m used to British beers and depending on where you’re from, my idea of high carbonation may be different to yours.
These amounts of white sugar are needed to prime beer:
|Volume of Beer (gallons/litres)||Light|
|1 gallon||0.4 oz||0.7 oz||1.1 oz|
|2 gallons||0.9 oz||1.4 oz||2.1 oz|
|3 gallon||1.4 oz||2.1 oz||3.2 oz|
|4 gallons||1.8 oz||2.8 oz||4.3 oz|
|5 gallons||2.3 oz||3.5 oz||5.3 oz|
|2 litres||7 g||10 g||16 g|
|4 litres||14 g||21 g||32 g|
|6 litres||20 g||31 g||48 g|
|8 litres||27 g||42 g||64 g|
|10 litres||34 g||52 g||80 g|
|12 litres||41 g||63 g||96 g|
|14 litres||48 g||73 g||112 g|
|16 litres||54 g||84 g||127 g|
|18 litres||61 g||94 g||144 g|
|20 litres||68 g||104 g||159 g|
As well as the flavour differences, using other sugars also affects how much carbonation you get.
These conversion factors take that into account:
The amounts in the table are for beer at 21°C /70°F. In very rough terms, add or subtract 2 grams / 0.03 oz ounces per °C/°F to account for temperature differences.
How To Add Priming Sugar
Finally, the important part. Adding priming sugar to your beer.
First make sure fermentation is over. If there are still fermentable sugars in the beer they will, most likely, eventually be used by the yeast.
In this scenario adding priming sugar could potentially cause over carbonation and the risk of exploding bottles. Strong beers are particularly susceptible.
Anyway, on bottling day, heat 450 ml water in a pan and dissolve in the priming sugar before boiling for ten minutes.
Leave to cool and pour into the beer, stirring gently to ensure even distribution.
With a bottling bucket it’s even easier. Just put the solution in the bucket before racking in the beer. It mixes itself as the bucket fills.
The key to consistent carbonation is mixing well so the priming sugar is distributed throughout the batch.
Phew. That’s enough for now.